Silylated Polyurethanes, Their Preparation and Use

ABSTRACT

A silylated polyurethane obtainable by a process comprising the following steps: (a) reacting at least one polyol with at least one triisocyanate to form a hydroxyl-terminated polyurethane prepolymer, and (b) reacting said polyurethane prepolymer with at least one isocyanatosilane of the formula (1): OCN—R—Si—(X)m(R1)3-m, wherein m is 0, 1 or 2, each R1 is independently from each other a hydroxyl group, an alkoxy group having 1 to 10 carbon atoms, an acyloxy group having 1 to 10 carbon atoms, or —OCH(R2)COOR3, wherein R2 is hydrogen or an alkyl group having 1 to 4 carbon atoms and R3 is a straight-chain or branched alkyl group having 1 to 8 carbon atoms, each X is independently from each other and optionally substituted hydrocarbon group having 1 to 10 carbon atoms, which can be interrupted by at least one heteroatom, and R is a difunctional organic group, to endcap the hydroxyl groups on said prepolymer with said isocyanatosilane. The silylated polyurethanes are suitable for use in a preparation as an adhesive, sealant, or coating agent.

The present invention relates to silylated polyurethanes, theirpreparation and their use in adhesives, sealants, and in coatingcompositions.

Polymer systems that possess reactive alkoxysilyl groups are known. Inthe presence of atmospheric moisture these alkoxysilane-terminatedpolymers are capable, already at room temperature, of condensing withone another with release of the alkoxy groups. What forms in thiscontext, depending on the concentration of alkoxysilyl groups and theirconfiguration, are principally long-chain polymers (thermoplastics),relatively wide-mesh three-dimensional networks (elastomers), or highlycrosslinked systems (thermosetting plastics).

The polymers generally comprise an organic backbone that carriesalkoxysilyl groups at the ends. The organic backbone can involve, forexample, polyurethanes, polyesters, polyethers, etc.

One-component, moisture-curing adhesives and sealants have played foryears a significant role in numerous technical applications. In additionto the polyurethane adhesives and sealants having free isocyanategroups, and the traditional silicone adhesives and sealants based ondimethylpolysiloxanes, the so-called modified silane adhesives andsealants have also been increasingly used recently. In this lattergroup, the main constituent of the polymer backbone is a polyether, andthe reactive and crosslinkable terminal groups are alkoxysilyl groups.The modified silane adhesives and sealants have the advantage, ascompared with the polyurethane adhesives and sealants, of being free ofisocyanate groups, in particular of monomeric diisocyanates; they arealso notable for a broad adhesion spectrum to a plurality of substrateswithout surface pretreatment using primers.

U.S. Pat. No. 4,222,925 A and U.S. Pat. No. 3,979,344 A describesiloxane-terminated organic sealant compositions, curable already atroom temperature, based on reaction products of isocyanate-terminatedpolyurethane prepolymers with 3-aminopropyltrimethoxysilane or2-aminoethyl- or 3-aminopropylmethoxysilane to yield isocyanate-freesiloxane-terminated prepolymers. Adhesives and sealants based on theseprepolymers have unsatisfactory mechanical properties, however,especially in terms of their elongation and breaking strength.

The methods set forth below for the manufacture of silane-terminatedprepolymers based on polyethers have already been described:

-   -   Copolymerization of unsaturated monomers with ones that comprise        alkoxysilyl groups, for example vinyltrimethoxysilane.    -   Grafting unsaturated monomers, such as vinyltrimethoxysilane,        onto thermoplastics such as polyethylene.    -   Hydroxyfunctional polyethers are converted in an ether        synthesis, using unsaturated chlorine compounds, e.g. allyl        chloride, into polyethers having terminal olefinic double        bounds, which in turn are reacted with hydrosilane compounds        that have hydrolyzable groups, for example HSi(OCH₃)₃, in a        hydrosilylation reaction under the catalytic influence of, for        example, transition metal compounds of the eighth group, to        yield silane-terminated polyethers.    -   In another method, the polyethers containing olefinically        unsaturated groups are reacted with a mercaptosilane such as,        for example, 3-mercaptopropyltrialkoxysilane.    -   In a further method, firstly hydroxyl-group-containing        polyethers are reacted with di- or polyisocyanates, which are        then in turn reacted with aminofunctional silanes or        mercaptofunctional silanes to yield silane-terminated        prepolymers.    -   A further possibility provides for the reaction of        hydroxyfunctional polyethers with isocyanatofunctional silanes        such as, for example, 3-isocyanatopropyltrimethoxysilane.

These manufacturing methods, and the use of the aforementionedsilane-terminated prepolymers in adhesive/sealant applications, arerecited e.g. in the following patent documents: U.S. Pat. No. 3,971,751A, EP-A-70475, DE-A-19849817, U.S. Pat. No. 6,124,387 A, U.S. Pat. No.5,990,257 A, U.S. Pat. No. 4,960,844 A, U.S. Pat. No. 3,979,344 A, U.S.Pat. No. 3,632,557 A, DE-A-4029504, EP-A-601021, or EP-A-370464.

EP 0931800 A1 describes the manufacture of silylated polyurethanes byreacting a polyol component having a terminal unsaturation of less than0.02 meq/g with a diisocyanate to yield a hydroxyl-terminatedprepolymer, and then reacting that with an isocyanatosilane of theformula OCN—R—Si—(X)_(m)(—OR¹)_(3-m), where m is 0, 1, or 2 and each R¹residue is an alkyl group having 1 to 4 carbon atoms and R is adifunctional organic group. According to the teaching of this document,such silylated polyurethanes exhibit a superior combination ofmechanical properties, and cure in reasonable amounts of time to yield alow-tack sealant without exhibiting excessive viscosity.

WO 2009/071542 A1 describes a method for preparing a silylatedpolyurethane, comprising reacting at least one polyol compound having amolecular weight of 4,000 to 30,000 g/mol and at least onemonofunctional compound with regard to isocyanates with at least onediisocyanate, in a stoichiometric excess of the sum of the polyolcompound(s) and monofunctional compound(s) relative to the diisocyanatecompound(s), whereby a hydroxyl-terminated polyurethane prepolymer isformed which is subsequently reacted with isocyanatosilane.

A need still exists for compositions based on silylated polyurethanesfor use in adhesives and sealants that exhibit better performance, inparticular, curing speed and mechanical strength after curing, and atthe same time show acceptable viscosity, allowing the compositions to beeasily applied. The object of the present invention is therefore toprovide silylated polyurethanes and respective compositions havingimproved curing speed while having acceptable mechanical strength andviscosity.

The manner in which the object is achieved by the invention may begathered from the Claims. It contains essentially of a silylatedpolyurethane obtainable by a process comprising the following steps:

-   -   (a) reacting at least one polyol with at least one triisocyanate        to form a hydroxyl-terminated polyurethane prepolymer; and    -   (b) reacting said polyurethane prepolymer with at least one        isocyanatosilane of the formula (1)

OCN—R—Si—(X)_(m)(R¹)_(3-m)   (1)

-   -   wherein    -   m is 0, 1 or 2,    -   each R¹ is independently from each other a hydroxyl group, an        alkoxy group having 1 to 10 carbon atoms, an acyloxy group        having 1 to 10 carbon atoms, or —OCH(R²)COOR³, wherein R² is        hydrogen or an alkyl group having 1 to 4 carbon atoms and R³ is        a straight-chain or branched alkyl group having 1 to 8 carbon        atoms,    -   each X is independently from each other and optionally        substituted hydrocarbon group having 1 to 10 carbon atoms, which        can be interrupted by at least one heteroatom, and    -   R is a difunctional organic group,    -   to endcap the hydroxyl groups on said prepolymer with said        isocyanatosilane.

According to the present invention, a hydroxyl-terminated polyurethaneprepolymer is obtained by reacting at least one polyol with at least onetriisocyanate.

A “polyol” is understood for purpose of the present invention as apolymer having at least two hydroxyl groups. In principle, a largenumber of polymers carrying at least two hydroxyl groups, such aspolyester polyols, polycaprolactones, polybutadienes or polyisoprenes aswell as hydrogenation products thereof, or also polyacrylates orpolymethacrylates, can be used as polyol compounds. Mixtures ofdifferent polyol compounds can also be used.

According to the present invention, a polyether polyol is preferablyused as the polyol. A “polyether” is understood for purpose of thepresent invention as a polymer whose repeating unit contains etherfunctionalities C—O—C in the main chain. Polymers having lateral ethergroups, such as cellulose ethers, starch ethers, and vinyl etherpolymers, as well as polyacetals, are therefore not covered by thisdefinition.

Polymers which contain polyethers as backbone have a flexible andelastic structure with which compositions that have outstanding elasticproperties can be manufactured. Polyethers are not only flexible intheir backbone, but also strong at the same time. Thus, for example,polyethers (in contrast to e.g., polyesters) are not attacked ordecomposed by water and bacteria.

In a preferred embodiment of the present invention, the polyol is apolyalkylene oxide, and more preferably polyethylene oxide and/orpolypropylene oxide.

Particularly advantageous viscoelastic properties can be achieved ifpolyethers having a narrow molecular weight distribution, and thus a lowpolydispersity are used as polymer backbones. These can be prepared, forexample, by so-called double metal cyanide (DMC) catalysis. Polyethersprepared in this way are notable for a particularly narrow molecularweight distribution, a high average molecular weight, and a very smallnumber of double bonds at the ends of the polymer chains.

In a specific embodiment of the present invention, the polyol is apolyether polyol having a polydispersity PD of less than 3, preferablyless than 1.7, more preferably less than 1.5, and most preferably lessthan 1.3.

According to the present invention, the number average molecular weightM_(n) of the polymer backbone of the polyol compounds is from 500 to20,000 g/mol (daltons), preferably from 2,000 to 18,000 g/mol, and mostpreferably 2,000 to 12,000 g/mol, the terminal unsaturation being lessthan 0.05 meq/g, preferably less than 0.04 meq/g, and more preferablyless than 0.02 meq/g.

These molecular weights are particularly advantageous because thesepolyols are readily available commercially and the resultingpolyurethanes or the compositions based thereon have a good balance ofviscosity (ease of processing) prior to curing and strength andelasticity after curing.

The number average molecular weight M_(n), as well as the weight averagemolecular weight M_(w), is determined by gel permeation chromatography(GPC, also known as SEC). This method is known to one skilled in theart. The polydispersity is derived from the average molecular weightsM_(w) and M_(n). It is calculated as PD=M_(w)/M_(n).

The ratio M_(w)/M_(n), also referred to as “polydispersity,” indicatesthe width of the molecular weight distribution and thus the differingdegrees of polymerization of the individual chains in polydispersepolymers. For many polymers and polycondensates, the applicablepolydispersity value is approximately 2. Strict monodispersity wouldexist for a value of 1. A low polydispersity (for example, less than1.5) indicates a comparatively narrow molecular weight distribution andthus the specific expression of properties associated with molecularweight, for example viscosity.

The triisocyanates suitable to convert the polyol compound into ahydroxyl-terminated polyurethane prepolymer can be derived fromdiisocyanates. Preferably, the triisocyanates are derived from HDI, TDI,MDI, PDI or IPDI, or mixtures thereof. In particular, followingtriisocyanates are most preferred.

According to the present invention, a stoichiometric excess of thehydroxyl groups of the polyol compound(s) with respect to the NCO groupsof the triisocyanate(s) or mixture of triisocyanates is used. Thepreferred molar ratio of the NCO groups to hydroxyl groups is from 0.05to 0.45, preferably from 0.1 to 0.45, and more preferably from 0.2 to0.45. This ensures that a polyurethane prepolymer having terminalhydroxyl groups is formed in step (a) according to the presentinvention.

The polyurethane prepolymer having terminal hydroxyl groups that isthereby formed is then reacted with at least one isocyanatosilane offormula (1):

OCN—R—Si—(X)_(m)(R¹)_(3-m),

to endcap the hydroxyl groups on said prepolymer with saidisocyanatosilane.In formula (1) m is 0, 1 or 2, preferably 0 or 1.

Each R¹ is independently from each other a hydroxyl group, an alkoxygroup having 1 to 10 carbon atoms, an acyloxy group having 1 to 10carbon atoms, or —OCH(R²)COOR³, wherein R² is hydrogen or an alkyl grouphaving 1 to 4 carbon atoms and R³ is a straight-chain or branched alkylgroup having 1 to 8 carbon atoms.

In a preferred embodiment of the present invention, each R¹ isindependently of each other an alkoxy or acyloxy group having 1 to 4carbon atoms. More preferably, each R¹ is independently of each other amethoxy or ethoxy group, particularly a methoxy group. Methoxy andethoxy groups, as comparatively small hydrolyzable groups with lowsteric bulk, are very reactive and thus enable a rapid cure even withlow use of catalyst. They are therefore of particular interest forsystems in which a rapid cure is desired, such as e.g. in adhesivesrequiring high initial adhesion. Particularly preferably, methoxy groupis used. The methoxy group displays the greatest reactivity among thealkoxy groups. Silyl groups of this type can therefore be used when aparticularly rapid cure is desired. Higher aliphatic residues, such asethoxy, already bring about lower reactivity of the terminal alkoxysilylgroup compared with methoxy groups and can advantageously be used todevelop gradual crosslinking rates.

In another preferred embodiment of the present invention, R¹ is—OCH(R²)COOR³, wherein preferably R² is methyl group and R³ is astraight-chain or branched alkyl group having 1 to 4 carbon atoms.

Each X is independently from each other an optionally substitutedhydrocarbon group having 1 to 10 carbon atoms, more preferably having 1to 4 carbon atoms, which can be interrupted by at least one heteroatom.“Interrupted by at least one heteroatom” means that the main chain of aresidue comprises, as a chain member, at least one atom that differsfrom carbon atom. Preferably, each X is independently from each other analkyl group having 1 to 10 carbon atoms, preferably an alkyl grouphaving 1 to 4 carbon atoms, particularly preferred methyl or ethyl.

In a preferred embodiment of the present invention, m in formula (1) hasthe value 0 or 1, so two or three hydroxyl- or hydrolysable groups,preferably alkoxy groups, are present. Generally, polymers that containdi- or trialkoxysilyl groups have highly reactive linking sites, whichmake rapid curing, high degrees of crosslinking and thus good finalstrengths possible. The particular advantage of dialkoxysilyl groups isthat the corresponding compositions are, after curing, softer and moreelastic than systems containing trialkoxysilyl groups. They aretherefore particularly suitable for utilization as sealants. Inaddition, they release less alcohol upon curing, and thus offer anapplication advantage from a physiological standpoint as well. Withtrialkoxysilyl groups, on the other hand, a higher degree ofcrosslinking can be achieved, which is particularly advantageous if ahard, solid substance is desired after curing. Trialkoxysilyl groups aremoreover more reactive, i.e. crosslink more quickly, and thus decreasethe quantity of catalyst required, and they have advantages in terms of“cold flow.”

R is a difunctional organic group, which can be a hydrocarbon grouphaving 1 to 12 carbon atoms, preferably an alkylene group having 1 to 6carbon atoms, and particularly preferably an alkylene group having 1 to3 carbon atoms. More preferably, R is a methylene, ethylene orn-propylene residue. Methylene and n-propylene residues are particularlypreferably used. In particular, compounds where R is methylene exhibithigh reactivity in the terminating silyl groups, which contributes toshorter curing and hardening times. If a propylene group is selected forR, these compounds then exhibit particularly high flexibility. Thecuring rate of formulations based on these polymers can also beinfluenced by means of the length of the hydrocarbon residues which formthe link between the polymer backbone and silyl residue.

The isocyanatosilanes listed below are particularly suitable:3-isocyanatopropyltrimethoxysilane,2-isocyanatoisopropyltrimethoxysilane,4-isocyanato-n-butyltrimethoxysilane,2-isocyanato-1,1-dimethylethyltrimethoxysilane,1-isocyanatomethyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane,2-isocyanato-2-methylethyltriethoxysilane,4-isocyanatobutyltriethoxysilane,2-isocyanato-1,1-dimethylethyltriethoxysilane,1-isocyanatomethyltriethoxysilane,3-isocyanatopropylmethyldimethoxysilane,3-isocyanatopropyldimethylmethoxysilane,3-isocyanatopropylphenylmethylmethoxysilane,1-isocyanatomethylmethyldimethoxysilane,3-isocyanatopropylethyldiethoxysilane,3-isocyanatopropylmethyldiethoxysilane,1-isocyanatomethylmethyldiethoxysilane, and mixtures thereof.

3-isocyanatopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane,1-isocyanatomethyltriethoxysilane,3-isocyanatopropylmethyldimethoxysilane,1-isocyanatomethylmethyldimethoxysilane,1-isocyanatomethylmethyldiethoxysilane, or mixtures thereof are moreparticularly preferred.

In a specific embodiment, according to the present invention,aforementioned process for preparing a silylated polyurethane comprisesfurther step of adding a catalyst. Suitable catalysts are well known. Inprinciple, any compound that can catalyze reaction of a hydroxyl groupand an isocyanato group to form a urethane bond can be used. Examplesthereof include tin compounds, like tin carboxylates such as dibutyltindilaurate (DBTL), dibutyltin diacetate, dibutyltin diethylhexanoate,dibutyltin dioctoate, dibutyltin dimethylmaleate, dibutyltindiethylmaleate, dibutyltin dibutylmaleate, dibutyltindiiosooctylmaleate, dibutyltin ditridecylmaleate, dibutyltindibenzylmaleate, dibutyltin maleate, dibutyltin diacetate, tin octaoate,dioctyltin distearate, dioctyltin dilaurate (DOTL), dioctyltindiethylmaleate, dioctyltin diisooctylmaleate, dioctyltin diacetate, andtin naphthenoate; tin alkoxides such as dibutyltin dimethoxide,dibutyltin diphenoxide, and dibutyltin diisoproxide; tin oxides such asdibutyltin oxide and dioctyltin oxide; reaction products betweendibutyltin oxides and phthalic acid esters, dibutyltinbisacetylacetonate; as well as non-tin compounds. The latter includetitanates such as tetrabutyl titanate and tetrapropyl titanate;organoaluminum compounds such as aluminum trisacetylacetonate, aluminumtrisethylacetoacetate, and diisopropoxyaluminum ethylacetoacetate;chelate compounds such as zirconium tetraacetylacetonate and titaniumtetraacetylacetonate; lead octanoate; amine compounds or salts thereofwith carboxylic acids, such as butylamine, octylamine, laurylamine,dibutylamines, monoethanolamines, diethanolamines, triethanolamine,diethylenetriamine, triethylenetetramine, oleylamines, cyclohexylamine,benzylamine, diethylaminopropylamine, xylylenediamine,triethylenediamine, guanidine, diphenylguanidine,2,4,6-tris(dimethylaminomethyl)phenol, morpholine, N-methylmorpholine,2-ethyl-4-methylimidazole, and 1,8-diazabicyclo-(5,4,0)-undecene-7(DBU), a low-molecular-weight polyamide resin obtained from an excess ofa polyamine and a polybasic acid, adducts of a polyamine in excess withan epoxy, silane adhesion promoters having amino groups, such as3-aminopropyltrimethoxysilane andaminoethyl)aminopropylmethyldimethoxysilane, as well as compounds ofpotassium, iron, indium, zinc, bismuth, and copper, preferablycarboxylates (salts of aliphatic carboxylic acids) or acetylacetonatesof potassium, iron, indium, zinc, bismuth, or copper. Preferably, thecatalyst is selected from the group consisting of compounds ofpotassium, iron, indium, zinc, bismuth, and copper, preferablycarboxylates (salts of aliphatic carboxylic acids) or acetylacetonatesof potassium, iron, indium, zinc, bismuth, or copper. C₄ to C₃₆saturated, mono- or polyunsaturated monocarboxylic acids cab be used, inparticular as aliphatic carboxylic acids. Examples thereof are:arachidic acid (n-eicosanoic acid), arachidonic acid(all-cis-5,8,11,14-eicosatetraenoic acid), behenic acid (docosanoicacid), butyric acid (butanoic acid), caproleic acid (9-decenoic acid),capric acid (n-decanoic acid), caproic acid (n-hexanoic acid), caprylicacid (n-octanoic acid), cerotic acid (hexacosanoic acid), cetoleic acid(cis-11-docosenoic acid), clupanodonic acid(all-cis-7,10,13,16,19-docosapentaenoic acid), eleostearic acid(trans-9-trans-11-cis-13-octadeca-9,11,13-trienoic acid), enanthic acid(1-hexanecarboxylic acid), erucic acid (cis-13-docosenoic acid),gadoleic acid (9-eicosenoic acid), gondoic acid (cis-11-eicosenoicacid), hiragonic acid (6,10,14-hexadecatrienoic acid), lauric acid(dodecanoic acid), lignoceric acid (tetracosanoic acid), linderic acid(cis-4-dodecenoic acid), linoleic acid ((cis,cis)-octadeca-9,12-dienoicacid), linolenic acid ((all-cis)-octadeca-9,12,15-trienoic acid),melissic acid (triacontanoic acid), montanic acid (octacosanoic acid),stearidonic acid (cis-6-cis-9-cis-12-cis-15-octadecatetraenoic acid),myristic acid (tetradecanoic acid), myristoleic acid(cis-9-tetradecenoic acid), naphthenic acid, neodecanoic acid, obtusilicacid (cis-4-decenoic acid), caprylic acid (n-octanoic acid), neooctanoicacid, oleic acid (cis-9-octadecenoic acid), palmitic acid(n-hexadecanoic acid), palmitoleic acid (cis-9-hexadecenoic acid),parinaric acid (9,11,13,15-octadecatetraenoic acid), petroselinic acid(cis-6-octadecenoic acid), physeteric acid (5-tetradecenoic acid),punicic acid (cis-9-trans-11-cis-13-octadeca-9,11,13-trienoic acid),scoliodonic acid (cis-5-cis-11-cis-14-eicosatrienoic acid), selacholeicacid (15-tetracosenoic acid), stearic acid (n-octadecanoic acid),tricosanoic acid, tsuzuic acid (cis-4-tetradecenoic acid),trans-vaccenic acid (trans-11-octadecenoic acid), palmitoleic acid(9-hexadecenoic acid). In addition to the acetylacetonates, chelates ofother β-dicarbonyl compounds of potassium, iron, indium, zinc, bismuth,or copper can also be used. Acetoacetic acid alkyl esters, dialkylmalonates, benzoylacetic esters, dibenzoylmethane, benzoylacetone, anddehydroacetoacetic acid may be recited concretely.

The present invention also provides a process for preparing a silylatedpolyurethane comprising the following steps:

-   -   (a) reacting at least one polyol with at least one triisocyanate        to form a hydroxyl-terminated polyurethane prepolymer; and    -   (b) reacting said polyurethane prepolymer with at least one        isocyanatosilane of the formula (1)

OCN—R—Si—(X)_(m)(R¹)_(3-m)  (1)

-   -   wherein    -   m is 0, 1 or 2,    -   each R¹ is independently from each other a hydroxyl group, an        alkoxy group having 1 to 10 carbon atoms, an acyloxy group        having 1 to 10 carbon atoms, or —OCH(R²)COOR³, wherein R² is        hydrogen or an alkyl group having 1 to 4 carbon atoms and R³ is        a straight-chain or branched alkyl group having 1 to 8 carbon        atoms,    -   each X is independently from each other an optionally        substituted hydrocarbon group having 1 to 10 carbon atoms, which        can be interrupted by at least one heteroatom, and    -   R is a difunctional organic group,    -   to endcap the hydroxyl groups on said prepolymer with said        isocyanatosilane.

The general, preferred, and particularly preferred embodiments describedfor the silylated polyurethane according to the present invention thusalso apply to the process for preparing the silylated polyurethaneaccording to the present invention.

The present invention also provides a curable composition, in particularan adhesive, sealant, or coating composition comprising at least onesilylated polyurethane according to the invention or obtainable by theaforementioned process according to the present invention.

The adhesive, sealant, coating composition according to the presentinvention can also contain, in addition to the aforementioned silylatedpolyurethane according to the present invention, further adjuvants andadditives that impart to these adhesive, sealant, coating compositionimproved elastic properties, improved elastic recovery, a sufficientlylong processing time, a fast curing time, and low residual tack.Included among these adjuvants and additives are, for example,catalysts, plasticizers, stabilizers, antioxidants, fillers, reactivediluents, drying agents, adhesion promoters and UV stabilizers,fungicides, flame retardants, rheological adjuvants, color pigments orcolor pastes, and/or optionally also, to a small extent, solvents.

A “plasticizer” is understood as a substance that decreases theviscosity of the compositions and thus facilitates processability. Theplasticizer is preferably selected from a fatty acid ester, adicarboxylic acid ester, an ester of OH-group-carrying or epoxidizedfatty acids, a fat, a glycolic acid ester, a benzoic acid ester, aphosphoric acid ester, a sulfonic acid ester, a trimellitic acid ester,an epoxidized plasticizer, a polyether plasticizer, a polystyrene, ahydrocarbon plasticizer, and a chlorinated paraffin, as well as mixturesof two or more thereof. Targeted selection of one of these plasticizers,or of a specific combination, can result not only in a decrease inviscosity and thus better processability, but also in furtheradvantageous properties of the composition according to the presentinvention, e.g. the gelling capability of the polymers, low-temperatureelasticity and/or low-temperature strength, or even antistaticproperties.

In principle, phthalic acid esters can be used as a plasticizer.However, these are not preferred due to their toxicological potential.

Of the polyether plasticizers, it is preferred to use end-cappedpolyethylene glycols, for example polyethylene or polypropylene glycoldi-C₁₋₄ alkyl ethers, in particular dimethyl or diethyl ethers ofdiethylene glycol or dipropylene glycol, as well as mixtures of two ormore thereof. Also suitable as plasticizers are, for example, esters ofabietic acid, butyric acid esters, acetic acid esters, propionic acidesters, thiobutyric acid esters, citric acid esters, and esters based onnitrocellulose and polyvinyl acetate, as well as mixtures of two or morethereof. Also suitable are, for example, the asymmetrical esters ofadipic acid monooctyl ester with 2-ethylhexanol (Edenol DOA, CognisDeutschland GmbH, Düsseldorf). The pure or mixed ethers ofmonofunctional, linear or branched C₄₋₁₆ alcohols, or mixtures of two ormore different ethers of such alcohols, for example dioctyl ethers(obtainable as Cetiol OE, Cognis Deutschland GmbH, Düsseldorf), are alsosuitable as plasticizers. Likewise, suitable in the context of thepresent invention as plasticizers are diurethanes, which can bemanufactured e.g. by reacting diols having OH terminal groups withmonofunctional isocyanates, by selecting the stoichiometry so thatsubstantially all the free OH groups react completely. A further methodfor manufacturing diurethanes involves reacting monofunctional alcoholswith diisocyanates, such that all the NCO groups react as completely aspossible.

Plasticizers can be additionally used in the composition at between 0and 40, by preference between 0 and 20 wt %, based on the total weightof the composition.

“Stabilizers” for purposes of this invention are to be understood asantioxidants, UV stabilizers, or hydrolysis stabilizers. Examplesthereof are the commercially usual sterically hindered phenols and/orthioethers and/or substituted benzotriazoles and/or amines of thehindered amine light stabilizer (HALS) type. It is preferred in thecontext of the present invention if a UV stabilizer that carries a silylgroup, and that is incorporated into the end product upon crosslinkingor curing, is used. The products Lowilite 75, Lowilite 77 (Great Lakes,USA) are particularly suitable for this purpose. Benzotriazoles,benzophenones, benzoates, cyanoacrylates, acrylates, sterically hinderedphenols, phosphorus, and/or sulfur can also be added.

The composition according to the present invention can contain up toapproximately 2 wt %, by preference approximately 1 wt % stabilizers. Inaddition, the composition according to the present invention can furthercontain up to approximately 7 wt %, in particular up to approximately 5wt % antioxidants.

The catalysts that can be used are all known compounds that can catalyzehydrolytic cleavage of the hydrolyzable groups of the silane groupings,as well as subsequent condensation of the Si—OH group to yield siloxanegroupings (crosslinking reaction and adhesion promotion function).Examples thereof are titanates such as tetrabutyl titanate andtetrapropyl titanate, tin carboxylates such as dibutyltin dilaurate(DBTL), dibutyltin diacetate, dibutyltin diethylhexanoate, dibutyltindioctoate, dibutyltin dimethylmaleate, dibutyltin diethylmaleate,dibutyltin dibutylmaleate, dibutyltin diiosooctylmaleate, dibutyltinditridecylmaleate, dibutyltin dibenzylmaleate, dibutyltin maleate,dibutyltin diacetate, tin octaoate, dioctyltin distearate, dioctyltindilaurate (DOTL), dioctyltin diethylmaleate, dioctyltindiisooctylmaleate, dioctyltin diacetate, and tin naphthenoate; tinalkoxides such as dibutyltin dimethoxide, dibutyltin diphenoxide, anddibutyltin diisoproxide; tin oxides such as dibutyltin oxide anddioctyltin oxide; reaction products between dibutyltin oxides andphthalic acid esters, dibutyltin bisacetylacetonate; organoaluminumcompounds such as aluminum trisacetylacetonate, aluminumtrisethylacetoacetate, and diisopropoxyaluminum ethylacetoacetate;chelate compounds such as zirconium tetraacetylacetonate and titaniumtetraacetylacetonate; lead octanoate; amine compounds or salts thereofwith carboxylic acids, such as butylamine, octylamine, laurylamine,dibutylamines, monoethanolamines, diethanolamines, triethanolamine,diethylenetriamine, triethylenetetramine, oleylamines, cyclohexylamine,benzylamine, diethylaminopropylamine, xylylenediamine,triethylenediamine, guanidine, diphenylguanidine,2,4,6-tris(dimethylaminomethyl)phenol, morpholine, N-methylmorpholine,2-ethyl-4-methylimidazole, und 1,8-diazabicyclo-(5,4,0)-undecene-7(DBU), a low-molecular-weight polyamide resin obtained from an excess ofa polyamine and a polybasic acid, adducts of a polyamine in excess withan epoxy, silane adhesion promoters having amino groups, such as3-aminopropyltrimethoxysilane andN-(β-aminoethyl)aminopropylmethyldimethoxysilane.

The catalyst, preferably mixtures of several catalysts, can be used in aquantity from 0.01 to approximately 5 wt % based on the entire weight ofthe composition.

The composition according to the present invention can additionallycontain fillers. Suitable here are, for example, chalk, lime powder,precipitated and/or pyrogenic silicic acid, zeolites, bentonites,magnesium carbonate, diatomite, alumina, clay, talc, titanium oxide,iron oxide, zinc oxide, sand, quartz, flint, mica, glass powder, andother ground mineral substances. Organic fillers can also be used, inparticular carbon black, graphite, wood fibers, wood flour, sawdust,cellulose, cotton, pulp, cotton, wood chips, chopped straw, chaff,ground walnut shells, and other chopped fibers. Short fibers such asglass fibers, glass filament, polyacrylonitrile, carbon fibers, Kevlarfibers, or polyethylene fibers can also be added. Aluminum powder islikewise suitable as a filler.

The pyrogenic and/or precipitated silicic acids advantageously have aBET surface area from 10 to 90 m²/g. When they are used, they do notcause any additional increase in the viscosity of the compositionaccording to the present invention, but do contribute to strengtheningthe cured composition.

It is likewise conceivable to use pyrogenic and/or precipitated silicicacids having a higher BET surface area, advantageously 100 to 250 m²/g,in particular 110 to 170 m²/g, as a filler. Because of the greater BETsurface area, the same effect, e.g. strengthening the cured composition,is achieved with a smaller weight proportion of silicic acid. Furthersubstances can thus be used to improve the composition according to thepresent invention in terms of different requirements.

Also suitable as fillers are hollow spheres having a mineral shell or aplastic shell. These can be, for example, hollow glass spheres that areobtainable commercially under the trade names Glass Bubbles®.Plastic-based hollow spheres, e.g. Expancel® or Dualite®, are describede.g. in EP 0 520 426 B1. They are made up of inorganic or organicsubstances and each have a diameter of 1 mm or less, preferably 500 μmor less.

Fillers that impart thixotropy to the composition are preferred for manyapplications. Such fillers are also described as rheological adjuvants,e.g. hydrogenated castor oil, fatty acid amides, or swellable plasticssuch as PVC. In order to be readily squeezable out of a suitabledispensing apparatus (e.g. a tube), such compositions possess aviscosity from 3000 to 150,000, preferably 40,000 to 80,000 mPas, oreven 50,000 to 60,000 mPas.

The fillers can be used by preference in a quantity from 1 to 80 wt %,by preference from 5 to 60 wt %, based on the total weight of thecomposition.

Examples of suitable pigments are titanium dioxide, iron oxides, orcarbon black.

In order to enhance shelf life even further, it is often advisable tofurther stabilize the composition according to the present inventionwith respect to moisture penetration using drying agents. A needoccasionally also exists to lower the viscosity of the adhesive orsealant according to the present invention for specific applications, byusing a reactive diluent. All compounds that are miscible with theadhesive or sealant with a reduction in viscosity, and that possess atleast one group that is reactive with the binder, can be used asreactive diluents.

The following substances can be used, for example, as reactive diluents:polyalkylene glycols reacted with isocyanatosilanes (e.g. Synalox100-50B, Dow), carbamatopropyltrimethoxysilane, alkyltrimethoxysilane,alkyltriethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, andvinyltrimethoxysilane (VTMO Geniosil XL 10, Wacker),vinyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane,octyltrimethoxysilane, tetraethoxysilane, vinyldimethoxymethylsilane(XL12, Wacker), vinyltriethoxysilane (GF56, Wacker),vinyltriacetoxysilane (GF62, Wacker), isooctyltrimethoxysilane (10Trimethoxy), isooctyltriethoxysilane (10 Triethoxy, Wacker),N-trimethoxysilylmethyl-O-methyl carbamate (XL63, Wacker),N-dimethoxy(methyl)silylmethyl-O-methyl carbamate (XL65, Wacker),hexadecyltrimethoxysilane, 3-octanoylthio-1-propyltriethoxysilane, andpartial hydrolysates of the aforementioned compounds.

Also, usable as reactive diluents are the following polymers of KanekaCorp.: MS S203H, MS S303H, MS SAT 010, and MS SAX 350.

Silane-modified polymers that are derived, for example, from thereaction of isocyanatosilane with Synalox grades can likewise be used.

In the same manner, the silylated polyurethanes according to the presentinvention can be used in a mixture with usual polymers or prepolymersknown per se, optionally with concurrent use of the aforementionedreactive diluents, fillers, and further adjuvants and additives. “Usualpolymers or prepolymers” can be selected in this context frompolyesters, polyoxyalkylenes, polyacrylates, polymethacrylates, ormixtures thereof; these can be free of groups reactive with siloxanegroups, but optionally can also comprise alkoxysilyl groups or hydroxylgroups.

A plurality of the aforementioned silane-functional reactive diluentshave at the same time a drying and/or adhesion-promoting effect in thecomposition. These reactive diluents may be used in quantities between0.1 and 15 wt %, by preference between 1 and 5 wt %, based on the totalweight of the composition.

Also suitable as adhesion promoters, however, are so-called tackifyingagents, such as hydrocarbon resins, phenol resins, terpene-phenolicresins, resorcinol resins or derivatives thereof, modified or unmodifiedresin acids or resin esters (abietic acid derivatives), polyamines,polyaminoamides, anhydrides, and anhydride-containing copolymers. Theaddition of polyepoxide resins in small quantities can also improveadhesion on many substrates. The solid epoxy resins having a molecularweight of over 700, in finely ground form, are then preferably used forthis. If tackifying agents are used as adhesion promoters, their natureand quantity depend on the adhesive/sealant composition and on thesubstrate onto which it is applied. Typical tackifying resins(tackifiers) such as, for example, terpene-phenolic resins or resin acidderivatives, may be used in concentrations between 5 and 20 wt %;typical adhesion promoters such as polyamines, polyaminoamides, orphenolic resins or resorcinol derivatives may be used in the rangebetween 0.1 and 10 wt %, based on the total weight of the composition.

The present invention also provides the use of the silylatedpolyurethane according to the present invention as an adhesive, sealant,coating composition, or for the production thereof.

In principle in the present invention, all features listed within thecontext of the present text, particularly the embodiments, proportionalranges, components and other features of the composition according tothe invention, of the method according to the invention and of the useaccording to the invention identified as preferred and/or special, canbe implemented in all possible and not mutually exclusive combinations,with combinations of features identified as preferred and/or specialalso being regarded as preferred and/or special.

EXAMPLES Example 1 (Ex 1)

Manufacture of a Silylated Polyurethane (Use of Triisocyanate):

384.02 g (33.88 mmol) of polypropylene ether polyol (Acclaim 12200,hydroxyl value=9.90) were dried in a 500 ml three-necked flask at 80-90°C. under vacuum. Under a nitrogen atmosphere, 0.28 g of bismuthneodecanoate (Borchi Kat 315) were added with stirring. Then, 2.52 g(4.52 mmol) of triisocyanate (Tolonate HDT-LV) were added (NCO/OHratio=0.2) with stirring. The mixture was left for one hour at 80-95° C.The conversion was accomplished with NCO monitoring, and as soon as thetheoretical NCO value of the prepolymer had been reached titrimetrically(% NCO=0), 13.18 g (62.69 mmol) of 3-isocyanatopropyltrimethoxysilane(Geniosil GF 40) were added with stirring and the mixture was left for afurther hour at 80-95° C. (% NCO=0.00 to 0.09). A star-shaped polymerwas obtained. The resulting polymer was stored in a moisture-proof glassvessel under a nitrogen atmosphere before being processed further into acurable composition. The viscosity was 41,200 mPas.

Comparative Example 1 (Comp 1)

Manufacture of a Silylated Polyurethane (Use of Diisocyanate):

A similar procedure to Example 1 was carried out except that HDI wasused instead of triisocyanate. The viscosity was 28,200 mPas. Detailsare summarized in Table 1.

Example 2 (Ex 2)

Manufacture of a Silylated Polyurethane (Use of Triisocyanate):

A similar procedure to Example 1 was carried out except that NCO/OHratio=0.4 and Acclaim 4200 (hydroxyl value=29.50) was used instead ofAcclaim 12200.

The viscosity was 78,600 mPas. Details are summarized in Table 1.

Comparative Example 2 (Comp 2)

Manufacture of a Silylated Polyurethane (Use of Diisocyanate):

A similar procedure to Example 2 was carried out except that HDI wasused instead of triisocyanate. The viscosity was 10,600 mPas. Detailsare summarized in Table 1.

TABLE 1 Ex 1 Comp 1 Ex 2 Comp 2 Acclaim 384.02 g 385.33 g 12200 (33.88mmol) (34.00 mmol) Acclaim 4200 357.13 g 364.02 g (93.90 mmol) (95.71mmol) Borchi Kat 0.28 g 0.28 g 0.28 g 0.28 g 315 Tolonate 2.52 g 13.95 gHDT-LV (4.52 mmol) (25.04 mmol) HDI 1.16 g 6.52 g (6.80 mmol) (38.28mmol) NCO/OH ratio 0.2 0.2 0.4 0.4 Geniosil GF 13.18 g 13.23 g 28.64 g29.18 g 40 (62.69 mmol) (62.90 mmol) (136.15 mmol) (138.78 mmol) % NCO0.00-0.09 0.00-0.09 0.00-0.25 0.00-0.25 after adding Geniosil GF 40Viscosity 41,200 mPas 28,200 mPas 78,600 mPas 10,600 mPas

Determination of the Viscosity of the Polymer:

The viscosity values were determined using Brookfield viscometer(DV-II+Pro), spindle 7, 20 rpm, at 23° C.

Examples A-F

Manufacture of Compositions Comprising a Silylated Polyurethane:

Each prepared silylated polyurethane according to above examples washeated for 24 hours at 23° C. and then 0.35 g ofN-(2-Aminoethyl)-3-aminopropyltrimethoxysilane (Geniosil GF 91) and 0.14g of DOTL or DBU were added to 34.51 g of each of the prepared polymer.This mixture was homogenized twice for 60 seconds at 2700 rpm in aSpeedMixer (DAC 150 FC).

The time to form a skin (skin over time/SOT) and mechanical strength(tensil strength and elongation) were determined for the abovementionedmixtures. The results are summarized in Table 2 below. DOTL was used inpreparing Examples A to D and DBU was used as a tin-free catalyst inpreparing Examples E to F.

TABLE 2 A B C D E F Silylated Ex 1 Comp 1 Ex 2 Comp 2 Ex 1 Comp 1Polyurethane SOT 14 min 16 min 22 min 1 h 21 min 33 min 44 min Tensil 0.88  0.85  1.10  0.89  0.80  0.76 Strength (N/mm²) Elongation 57.9861.75 43.28 39.38 55.53 53.88 (%)

Determination of the Skin-Over Time (SOT) and Mechanical Strength(Tensil Strength and Elongation):

The aforementioned mixtures were homogenized and applied in a frame(50×130×2 mm). Each mixture was evenly distributed so that the frame canbe completely filled. A thin polymer film was thereby obtained. The timeto form a skin (skin-over time/SOT) was determined for thesecompositions using a tool which has a rounded spatula at the tip (150×5mm). The tip of the spatula was gently contacted with the surface of thepolymer film every 1 to 5 minutes and removed carefully. The SOT wasmeasured once no more residue of the formulation remains on the spatulawhen removing it from the surface of the polymer film. Then, theresulting string must be removed from the spatula without residue. Thepolymer film returned to its original shape. In examining the SOT adifferent part of the surface of the polymer film must be used everytime. The test was performed at 23° C. and 50% relative humidity.

After being stored for 7 days (23° C., 50% relative humidity), fourspecimens were prepared from the polymer film and punched using a Mäderpress (APK T3-5-40) and a punching tool unit according to DIN 53504-S3A.The mechanical data were determined by reference to DIN 53504:2009-10.Each specimen was set to the initial test position using a pre-load of0.05 MPa and a speed rate of 40 mm/min. Actual measurement was doneusing a speed rate of 50 mm/min.

The examples show that the mixtures A, C, and E containing a silylatedpolyurethane according the present invention (Examples 1 to 2), showreasonable viscosity, exhibit significantly shorter SOT than mixturescomprising a silylated polyurethane according to the ComparativeExamples 1 to 2, while having good mechanical strength (tensil strengthand elongation). In addition, comparison of Examples E and F shows thateven in case of using non-tin catalyst the mixture containing asilylated polyurethane according the present invention also exhibitsshort SOT and good mechanical properties.

1. A silylated polyurethane obtained by a process comprising thefollowing steps: (a) reacting at least one polyol with at least onetriisocyanate to form a hydroxyl-terminated polyurethane prepolymer; and(b) reacting the hydroxyl-terminated polyurethane prepolymer with atleast one isocyanatosilane of formula (1) to endcap the hydroxyl groupson the hydroxyl-terminated polyurethane prepolymer with theisocyanatosilane,OCN—R—Si—(X)_(m)(R¹)_(3-m)  (1) wherein m is 0, 1 or 2, each R¹ isindependently from each other a hydroxyl group, an alkoxy group having 1to 10 carbon atoms, an acyloxy group having 1 to 10 carbon atoms, or—OCH(R²)COOR³, wherein R² is hydrogen or an alkyl group having 1 to 4carbon atoms and R³ is a straight-chain or branched alkyl group having 1to 8 carbon atoms, each X is independently from each other an optionallysubstituted hydrocarbon group having 1 to 10 carbon atoms, which can beinterrupted by at least one heteroatom, and R is a difunctional organicgroup.
 2. The silylated polyurethane according to claim 1, wherein amolar ratio of the NCO groups of the triisocyanate to hydroxyl groups ofthe polyol is from 0.05 to 0.45.
 3. The silylated polyurethane accordingto claim 1, wherein said polyol is a polyether polyol.
 4. The silylatedpolyurethane according to claim 1, wherein said polyol has a numberaverage molecular weight of from 500 to 20,000 g/mol.
 5. The silylatedpolyurethane according to claim 1, wherein said triisocyanate is derivedfrom HDI, TDI, MDI, PDI, IPDI, or mixtures thereof.
 6. The silylatedpolyurethane according to claim 1, wherein said isocyanatosilane isselected from the group consisting of3-isocyanatopropyltrimethoxysilane,2-isocyanatoisopropyltrimethoxysilane,4-isocyanato-n-butyltrimethoxysilane,2-isocyanato-1,1-dimethylethyltrimethoxysilane,1-isocyanatomethyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane,2-isocyanato-2-methylethyltriethoxysilane,4-isocyanatobutyltriethoxysilane,2-isocyanato-1,1-dimethylethyltriethoxysilane,1-isocyanatomethyltriethoxysilane,3-isocyanatopropylmethyldimethoxysilane,3-isocyanatopropyldimethylmethoxysilane,3-isocyanatopropylphenylmethylmethoxysilane,1-isocyanatomethylmethyldimethoxysilane,3-isocyanatopropylethyldiethoxysilane,3-isocyanatopropylmethyldiethoxysilane,1-isocyanatomethylmethyldiethoxysilane, and mixtures thereof.
 7. Thesilylated polyurethane according to claim 1, wherein said processcomprises further step of adding a catalyst.
 8. A process for preparinga silylated polyurethane comprising the following steps: (a) reacting atleast one polyol with at least one triisocyanate to form ahydroxyl-terminated polyurethane prepolymer; and (b) reacting thehydroxyl-terminated polyurethane prepolymer with at least oneisocyanatosilane of formula (1) to endcap the hydroxyl groups on thehydroxyl-terminated polyurethane prepolymer with the isocyanatosilane,OCN—R—Si—(X)_(m)(R¹)_(3-m)   (1) wherein m is 0, 1 or 2, each R¹ isindependently from each other a hydroxyl group, an alkoxy group having 1to 10 carbon atoms, an acyloxy group having 1 to 10 carbon atoms, or—OCH(R²)COOR³, wherein R² is hydrogen or an alkyl group having 1 to 4carbon atoms and R³ is a straight-chain or branched alkyl group having 1to 8 carbon atoms, each X is independently from each other an optionallysubstituted hydrocarbon group having 1 to 10 carbon atoms, which can beinterrupted by at least one heteroatom, and R is a difunctional organicgroup.
 9. An adhesive, sealant, or coating composition comprising thesilylated polyurethane according to claim
 1. 10. A silylatedpolyurethane that is the reaction product of a mixture comprising: (a)the hydroxyl terminated polyurethane prepolymer reaction product of amixture comprising at least one polyol and at least one triisocyanate;and (b) at least one isocyanatosilane of formula (1)OCN—R—Si—(X)_(m)(R¹)_(3-m)  (1) wherein m is 0, 1 or 2, each R¹ isindependently from each other a hydroxyl group, an alkoxy group having 1to 10 carbon atoms, an acyloxy group having 1 to 10 carbon atoms, or—OCH(R²)COOR³, wherein R² is hydrogen or an alkyl group having 1 to 4carbon atoms and R³ is a straight-chain or branched alkyl group having 1to 8 carbon atoms, each X is independently from each other an optionallysubstituted hydrocarbon group having 1 to 10 carbon atoms, which can beinterrupted by at least one heteroatom, and R is a difunctional organicgroup.